This invention relates to scanning systems such as infrared scanning systems and particularly to a highly accurate mirror position sensing system.
In sensor systems such as IR (infrared) scanning and display systems in which a moving mirror is utilized to scan a scene being interrogated, the instantaneous position of the mirror is required, for example, to correct the image distortion of the scene and to enhance the picture in the processor. Conventionally, detection of the mirror position requires a highly constant scan mirror velocity, two sensors for forward and backward scanning of the mirror plus considerable electronic circuitry to respond to the sensors. Further, conventional systems are typically unable to totally compensate for variations of mirror speed. A simplified and highly accurate scanning mirror position sensor capable of indicating position despite mirror speed variations would be a substantial advantage to the art. An application describing a mirror position sensing system that operates independent of speed variations in Ser. No. 809,149, "Scan Mirror Position Determining System," by Robert N. Sato, filed June 22, 1977, and assigned to the same assignee as the subject application. This referenced application teaches a system utilizing the back side of the scanning mirror to apply a light beam to a plurality of detectors that are arranged to provide a Gray code.